Hemoglobin, coupled oxidation

Although the coupled oxidation reaction closely resembles the enzymatic reaction, it may not be identical. One clear difference is that heme free in solution is oxidized at all four meso positions 40), heme in myoglobin only at the a-meso position 6, 46) and heme in hemoglobin at the a- and -positions 6, 46). Prior to the observation that hemin in... 

As shown, a reversible redox couple for immobilized protein was observed. Furthermore, the absorption bond of hemoglobin cobalt- oxide fdm (Curve b) is 407 nm similar to that of hemoglobin in pH buffer solution (Curve a), indicates no observable denaturation of hemoglobin happened on cobalt oxide film The immobilized hemoglobin shows excellent stability at wide pH range with high electron transfer rate constant, 1.4 0.1 s 1. 

Other reactions of hemoglobin also permit a free radical interpretation, notably the coupled oxidation with ascorbic acid by molecular 02 which yields choleglobin, but further discussion requires a full kinetic analysis. Even though the denaturation reactions described above have not been examined kinetically it is worth emphasizing that their chief features can be explained by the formation of 02- as in the mechanism advanced for the autoxidation. The liberation of an activated O2 molecule is no longer required—02 is the active oxygen. 

Ahlquist, D.A. and Schwartz, S., Use of leuco-dyes in tiie quantitative colorimetric microdetermination of hemoglobin and otiierheme compounds, Clin. Chem. 21, 362—369, 1975 Josephy, P.D., Benzidine mechanisms of oxidative activation and mutagensis. Fed. Proc. 45, 2465-2470, 1986 Choudhary, G., Human health perspectives on environmental exposure to benzidine areview, Chemosphere 32,267—291,1996 Madeira, R, Nunes, M.R., Borges, C. et al., Benzidine photodegradation a mass spectrometry and UV spectroscopy combined study. Rapid Commun. Mass Spectrom. 19, 2015—2020, 2005 Saitoh, T, Yoshida, S., and Ichikawa, J., N htiialene-l,8-diylbis(diphenylmethylium) as an organic two-electron oxidant benzidine syntiiesis via oxidative self-coupling of A,iV-dialkylanilines, J. Org. Chem. 71, 6414-6419, 2006. 

This composite satellite image displays areas on the surface of the Earth where chlorophyll-bearing plants are located. Chlorophyll, which is one of nature s most important biomolecules, is a member of a class of compounds called porphyrins. This Glass also includes hemoglobin and cytochrome c, which is discussed in Feature 19-1. Many analytical techniques have been used to measure the chemical and physical properties of chlorophyll to explore Its role in photosynthesis. The redox titration of chlorophyll with other standard redox couples reveals the oxidation/ reduction properties of the molecule that help explain the photophysics of the complex process that green plants use to oxidize water to molecular oxygen. 

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